Zoom lens

ABSTRACT

A zoom lens includes sequentially from an object side, a positive first lens group; a negative second lens group; a diaphragm; a positive third lens group; a positive fourth lens group; and a positive fifth lens group, wherein a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied. SLW is a distance from the diaphragm at a wide angle edge to an imaging plane; SLM is a distance from the diaphragm at an intermediate zoom position to the imaging plane; SLT is a distance from the diaphragm at a telephoto edge to the imaging plane; FW is optical system focal length for infinity at the wide angle edge; and F14t is a combined focal length for the first to the fourth lens groups at the telephoto edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-158657, filed on Jul. 3, 2009, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a large diameter, high power zoom lens.

2. Description of the Related Art

Conventionally, a large number of variable focus lenses aimed at achieving high zoom ratios have been proposed. Such variable focus lenses, for example, include sequentially from an object side at least a positive first lens group, a negative lens group, a positive third lens group, a positive fourth lens group, and a positive fifth lens group, and focuses an image of an object by moving the fifth lens group (refer to Japanese Patent Application Laid-Open Publication Nos. 2005-345714 and 2001-75008).

The zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2005-345714 includes at least 5 lens groups that are positive, negative, positive, positive, and positive respectively from the object side, has an angle of view exceeding 62° at the wide angle edge, and realizes a zoom ratio of 11.3 or greater. Further, the zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2001-75008 includes at least 6 lens groups that are positive, negative, positive, positive, negative, and positive respectively from the object side, has an angle of view exceeding 42° at the wide angle edge, and realizes a zoom ratio of 11.1 or greater.

Although the zoom lenses recited respectively in Japanese Patent Application Laid-Open Publication Nos. 2005-345714 and 2001-75008 realize high zoom ratios of 11 or greater, the F number also significantly increases accompanying zoom and thus, enlarged images become dark. Furthermore, the angle of view is insufficient.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least solve the above problems in the conventional technologies.

A zoom lens according to one aspect of the present invention includes sequentially from an object side, a positive first lens group; a negative second lens group; a diaphragm; a positive third lens group; a positive fourth lens group; and a positive fifth lens group, wherein a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied. SLW is a distance from the diaphragm at a wide angle edge to an imaging plane; SLM is a distance from the diaphragm at an intermediate zoom position to the imaging plane; SLT is a distance from the diaphragm at a telephoto edge to the imaging plane; FW is optical system focal length for infinity at the wide angle edge; and F14t is a combined focal length for the first to the fourth lens groups at the telephoto edge.

The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view (along the optical axis) of a zoom lens according to a first example;

FIG. 2 is a diagram of various types of aberration of the zoom lens according to the first example;

FIG. 3 is a cross sectional view (along the optical axis) of a zoom lens according to a second example;

FIG. 4 is a diagram of various types of aberration of the zoom lens according to the second example;

FIG. 5 is a cross sectional view (along the optical axis) of a zoom lens according to a third example;

FIG. 6 is a diagram of various types of aberration of the zoom lens according to the third example;

FIG. 7 is a cross sectional view (along the optical axis) of a zoom lens according to a fourth example;

FIG. 8 is a diagram of various types of aberration of the zoom lens according to the fourth example;

FIG. 9 is a cross sectional view (along the optical axis) of a zoom lens according to a fifth example;

FIG. 10 is a diagram of various types of aberration of the zoom lens according to the fifth example;

FIG. 11 is a cross sectional view (along the optical axis) of a zoom lens according to a sixth example; and

FIG. 12 is a diagram of various types of aberration of the zoom lens according to the sixth example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, exemplary embodiments according to the present invention are explained in detail below.

The zoom lens according to the embodiment includes sequentially from the object side, a positive first lens group, a negative second lens group, a diaphragm, a positive third lens group, a positive fourth lens group, and a positive fifth lens group. By moving any among the second to the fourth lens groups along the optical axis, the zoom lens zooms from the wide angle edge to the telephoto edge. By moving the fifth lens group along the optical axis, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image.

One object of the present invention is to provide a large diameter, high zoom ratio zoom lens that ensures a wide angle of view and is able to maintain a small F number over the entire zoom range. To achieve this object, various conditions are set as indicated below.

The zoom lens according to the embodiment preferably satisfies the following conditional expression, where a distance from the diaphragm at the wide angle edge to the imaging plane is SLW, a distance from the diaphragm at the intermediate zoom position to the imaging plane is SLM, and a distance from the diaphragm at the telephoto edge to the imaging plane is SLT, where the focal length of the entire optical system for infinity at the wide angle edge is FW.

0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0  (1)

Conditional expression (1) prescribes a condition to reduce the effective diameter of the first lens group while maintaining an angle of view of 70° or greater at the wide angle edge. By satisfying conditional expression (1), both wide angle and a reduction of the diameter of the first lens group are achievable. Below the lower limit of conditional expression (1), the effective diameter of the first lens group at the intermediate zoom position of the zoom lens becomes too large, making it difficult to achieve a reduction in the diameter of the first lens group while maintaining a wide angle of view. Above the upper limit of conditional expression (1), the effective diameter of the fifth lens group, which has a function of focusing, must be increased, resulting in an increased diameter of the fifth lens group and hence, the disadvantage of reduced focusing speed.

Further, the zoom lens according to the embodiment preferably satisfies the following conditional expression, where a combined focal length of the first to the fourth lens groups at the telephoto edge is F14.

F14t≦0  (2)

Conditional expression (2) prescribes a condition to reduce the effective diameters of the fourth and the fifth lens groups disposed behind the diaphragm, while maintaining a large diameter at the telephoto edge. By satisfying conditional expression (2), a bright image can be obtained even at the telephoto edge while at the same time, a reduction in the diameters of the fourth and the fifth lens groups can be achieved. Above the upper limit of conditional expression (2), reduction of the diameters of the fourth and the fifth lens groups becomes difficult and thus, values exceeding the upper limit are undesirable.

The zoom lens according to the embodiment preferably satisfies the following conditional expression, where among the lenses in the second lens group, the lens that is farthest on the object side has a surface on the object side that is formed to be aspheric, deviation of the paraxial curvature radius and the aspheric shape is S10 at a height that is 10% of the effective diameter of the aspheric surface, and the height of 10% of the effective diameter is H.

S10/H≧0.005  (3)

Conditional expression (3) prescribes the aspheric shape of the lens in the second lens group. In the second lens group, by forming the surface on the object side of the lens that is farthest on the object side to have an aspheric surface satisfying conditional expression (3), various types of aberration such as spherical aberration, astigmatism, distortion, etc. can be corrected well, over the entire zoom range. In the second lens group, if the surface on the object side of the lens that is farthest on the object side does not have an aspheric surface satisfying conditional expression (3), the correction of various types of aberration cannot be sufficiently performed.

As described above, by satisfying conditional expression (1) and (2), diameter reduction and maintenance of a wide angle of view are possible, making the zoom lens according to the present embodiment a large diameter zoom lens that is capable of high zoom ratios. Furthermore, in the second lens group, by forming the surface on the object side of the lens that is farthest on the object side to have an aspheric surface satisfying conditional expression (3), various types of aberration can be effectively corrected over the entire zoom range without sacrificing the compactness of the optical system.

FIG. 1 is a cross sectional view (along the optical axis) of a zoom lens according to a first example. The zoom lens includes, sequentially from a non-depicted object side, a positive first lens group G₁₁, a negative second lens group G₁₂, a positive third lens group G₁₃, a positive fourth lens group G₁₄; a positive fifth lens group G₁₅, and a negative sixth G₁₆. Further, a diaphragm STP is disposed between the second lens group G₁₂ and the third lens group G₁₃. A cover glass CG (or filter) is disposed between the sixth lens group G₁₆ and an imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, an optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₁₁ includes, sequentially from the object side, a negative lens L₁₁₁, a positive lens L₁₁₂, a positive lens L₁₁₃, and a positive lens L₁₁₄. The negative lens L₁₁₁ and the positive lens L₁₁₂ are cemented together.

The second lens group G₁₂ includes, sequentially from the object side, a negative lens L₁₂₁, a negative lens L₁₂₂, a positive lens L₁₂₃, and a negative lens L₁₂₄. The negative lens L₁₂₂ and the positive lens L₁₂₃ are cemented together. Further, a surface on the object side of the negative lens L₁₂₁ is formed to be aspheric.

The third lens group G₁₃ includes, sequentially from the object side, a positive lens L₁₃₁ and a negative lens L₁₃₂ that are cemented together.

The fourth lens group G₁₄ includes, sequentially from the object side, a positive lens L₁₄₁, a positive lens L₁₄₂ and a negative lens L₁₄₃. A surface on the object side of the positive lens L₁₄₂ is aspheric. Further, the positive lens L₁₄₂ and the negative lens L₁₄₃ are cemented together.

The fifth lens group G₁₅ includes, sequentially from the object side, a positive lens L₁₅₁, a negative lens L₁₅₂, and a positive lens L₁₅₃. Both surfaces of the positive lens L₁₅₁ are aspheric. Further, the negative lens L₁₅₂ and the positive lens L₁₅₃ are cemented together.

The sixth lens group G₁₆ includes, sequentially from the object side, a negative lens L₁₆₁ and a positive lens L₁₆₂ that are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₁₂, the third lens group G₁₃, and the fourth lens group G₁₄ along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G₁₅ along the optical axis. The first lens group G₁₁ and the sixth lens group G₁₆ remain fixed.

Various values related to the zoom lens according to the first example are indicated below.

focal length of entire zoom lens=8.42 (wide angle edge) to 22.75 (intermediate zoom position) to 62.70 (telephoto edge) F number=2.85 angle of view (2ω)=70.1° (wide angle edge) to 27.64° (intermediate zoom position) to 10.26° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=64.382 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=74.473 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=62.736 focal length (FW) of entire optical system for infinity at wide angle edge=8.42

(SLM−(SLW+SLT)/2)/FW=1.296 (Values Related to Conditional Expression (2))

F14t=−274.22

(Values Related to Conditional Expression (3))

deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₁₂=0.550 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₁₂=29.700

S10/H=0.019

r₁=134.2328

d₁=1.6500 nd₁=1.80610 υd₁=33.27

r₂=60.3060

d₂=8.6001 nd₂=1.49700 υd₂=81.61

r₃=607.0146

d₃=0.1500

r₄=60.8304

d₄=6.2517 nd₃=1.49700 υd₃=81.61

r₅=281.3437

d₅=0.1500

r₆=63.3658

d₆=4.3249 nd₄=1.61800 υd₄=63.39

r₇=146.8250

d₇=0.9000 (wide angle edge) to 25.4067 (intermediate zoom position) to 45.0224 (telephoto edge)

r₈=309.6078 (aspheric surface)

d₈=0.3000 nd₅=1.53610 υd₅=41.00

r₉=149.0172

d₉=1.2000 nd₆=1.88300 υd₆=40.80

r₁₀=16.0674

d₁₀=7.6090

r₁₁=−26.6578

d₁₁=1.0000 nd₇=1.49700 υd₇=81.61

r₁₂=26.6578

d₁₂=5.4742 nd₈=1.90366 υd₈=31.31

r₁₃=−35.0742

d₁₃=1.2590

r₁₄=−22.9708

d₁₄=0.8000 nd₉=1.48749 υd₉=70.44

r₁₅=37.6804

d₁₅=45.9494 (wide angle edge) to 11.3508 (intermediate zoom position) to 3.4718 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.2000

r₁₇=44.1399

d₁₇=3.0954 nd₁₀=1.61800 υd₁₀=63.39

r₁₈=−16.0964

d₁₈=0.8000 nd₁₁=1.56732 υd₁₁=42.84

r₁₉=81.5134

d₁₉=6.2937 (wide angle edge) to 16.3856 (intermediate zoom position) to 4.6489 (telephoto edge)

r₂₀=17.4600

d₂₀=2.5000 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=57.9358

d₂₁=0.1500

r₂₂=27.8066 (aspheric surface)

d₂₂=2.4494 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=−99.1785

d₂₃=0.8000 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=15.9500

d₂₄=12.7128 (wide angle edge) to 6.7148 (intermediate zoom position) to 5.8692 (telephoto edge)

r₂₅=16.7429 (aspheric surface)

d₂₅=6.0463 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−31.9401 (aspheric surface)

d₂₆=0.1500

r₂₇=−86.2525

d₂₇=1.0000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=19.3000

d₂₈=6.8470 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−19.3000

d₂₉=8.2372 (wide angle edge) to 14.2351 (intermediate zoom position) to 15.0808 (telephoto edge)

r₃₀=−14.5534

d₃₀=0.8000 nd₁₈=1.80610 υd_(n)=33.27

r₃₁=75.8757

d₃₁=3.0000 nd₁₉=1.92286 υd₁₉=20.88

r₃₂=−19.9968

d₃₂=0.8000

r₃₃=∞

d₃₃=1.0000 nd₂₀=1.51680 υd₂₀=64.20

r₃₄=∞

d₃₄=4.4970 (wide angle edge) to 4.5081 (intermediate zoom position) to 4.4907 (telephoto edge)

r₃₅=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=344.0097, A=1.13202×10⁻⁵, B=−2.26973×10⁻⁸, C=6.79562×10⁻¹¹, D=−9.81657×10⁻¹⁴

(twenty-second plane)

K=−0.9482, A=−5.12429×10⁻⁶, B=−1.21508×10⁻⁷, C=1.69189×10⁻⁹, D=−9.91420×10⁻¹²

(twenty-fifth plane)

K=−0.1842, A=−2.67312×10⁻⁵, B=1.32767×10⁻⁷, C=−9.76063×10⁻¹⁰, D=−4.41242×10⁻¹³

(twenty-sixth plane)

K=0.0482, A=3.21221×10⁻⁵, B=1.32020×10⁻⁷, C=−1.61331×10⁻⁹, D=3.26315×10⁻³²

FIG. 2 is a diagram of various types of aberration of the zoom lens according to the first example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 2 indicating astigmatism, represent aberration with respect to a sagittal image plane and a meridional image plane, respectively.

FIG. 3 is a cross sectional view (along the optical axis) of a zoom lens according to a second example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G₂₁, a negative second lens group G₂₂, a positive third lens group G₂₃, a positive fourth lens group G₂₄, a positive fifth lens group G₂₅, and a negative sixth lens group G₂₆. Further, the diaphragm STP is disposed between the second lens group G₂₂ and the third lens group G₂₃. The cover glass CG (or filter) is disposed between the sixth lens group G₂₆ and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₂₁ includes, sequentially from the object side, a negative lens L₂₁₁, a positive lens L₂₁₂, a positive lens L₂₁₃, and a positive lens L₂₁₄. The negative lens L₂₁₁ and the positive lens L₂₁₂ are cemented together.

The second lens group G₂₂ includes, sequentially from the object side, a negative lens L₂₂₁, a negative lens L₂₂₂, a positive lens L₂₂₃, and a negative lens L₂₂₄. The negative lens L₂₂₂ and the positive lens L₂₂₃ are cemented together. Further, a surface on the object side of the negative lens L₂₂₁ is formed to be aspheric.

The third lens group G₂₃ includes, sequentially from the object side, a positive lens L₂₃₁ and a negative lens L₂₃₂ that are cemented together.

The fourth lens group G₂₄ includes, sequentially from the object side, a positive lens L₂₄₁, a positive lens L₂₄₂, and a negative lens L₂₄₃. A surface on the object side of the positive lens L₂₄₂ is aspheric. Further, the positive lens L₂₄₂ and the negative lens L₂₄₃ are cemented together.

The fifth lens group G₂₅ includes, sequentially from the object side, a positive lens L₂₅₁, a negative lens L₂₅₂, and a positive lens L₂₅₃. Both surfaces of the positive lens L₂₅₁ are aspheric. Further, the negative lens L₂₅₂ and the positive lens L₂₅₃ are cemented together.

The sixth lens group G₂₆ includes, sequentially from the object side, a negative lens L₂₆₁ and a positive lens L₂₆₂ that are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₂₂, the third lens group G₂₃, and the fourth lens group G₂₄ along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G₂₅ along the optical axis. The first lens group G₂₁ and the sixth lens group G₂₆ remain fixed.

Various values related to the zoom lens according to the second example are indicated below.

focal length of entire zoom lens=7.58 (wide angle edge) to 22.75 (intermediate zoom position) to 54.25 (telephoto edge) F number=2.40 angle of view (2ω)=75.9° (wide angle edge) to 27.22° (intermediate zoom position) to 11.87° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=60.888 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=76.383 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=66.587 focal length (FW) of entire optical system for infinity at wide angle edge=7.58

(SLM−(SLW+SLT)/2)/FW=1.669 (Values Related to Conditional Expression (2))

F14t=−167.758

(Values Related to Conditional Expression (3))

deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₂₂=0.809 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₂₂=31.300

S10/H=0.026

r₁=207.0000

d₁=1.6000 nd₁=1.90366 υd₁=31.31

r₂=68.9000

d₂=8.5664 nd₂=1.49700 υd₂=81.61

r₃=970.0000

d₃=0.1500

r₄=74.8900

d₄=6.1637 nd₃=1.49700 υd₃=81.61

r₅=370.0000

d₅=0.1500

r₈=62.6000

d₆=4.9877 nd₄=1.75700 υd₄=47.71

r₇=167.0000

d₇=1.0000 (wide angle edge) to 30.0775 (intermediate zoom position) to 47.5000 (telephoto edge)

r₈=442.8586 (aspheric surface)

d₈=0.2000 nd₅=1.53920 υd₅=41.21

r₉=103.6181

d₉=1.0000 nd₆=1.88300 υd₆=40.80

r₁₀=15.0018

d₁₀=9.0225

r₁₁=−24.0001

d₁₁=0.7000 nd₇=1.49700 υd₇=81.61

r₁₂=38.3759

d₁₂=5.7015 nd₈=1.90366 υd₈=31.31

r₁₃=−28.8899

d₁₃=0.5664

r₁₄=−24.0930

d₁₄=0.7000 nd₉=1.49700 υd₉=81.61

r₁₅=71.3234

d₁₅=55.3046 (wide angle edge) to 10.7360 (intermediate zoom position) to 3.1168 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.2000

r₁₇=44.5619

d₁₇=4.2309 nd₁₀=1.61800 υd₁₀=63.39

r₁₈=−20.7679

d₁₈=0.6000 nd₁₁=1.56732 υd₁₁=42.84

r₁₉=53.6764

d₁₉=4.2562 (wide angle edge) to 13.7276 (intermediate zoom position) to 1.5000 (telephoto edge)

r₂₀=19.4936

d₂₀=2.7141 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=46.1822

d₂₁=1.4399

r₂₂=20.7222 (aspheric surface)

d₂₂=3.0000 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=629.2796

d₂₃=0.6000 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=16.2600

d₂₄=7.7197 (wide angle edge) to 6.9446 (intermediate zoom position) to 5.8651 (telephoto edge)

r₂₅=17.1547 (aspheric surface)

d₂₅=5.0000 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−44.7408 (aspheric surface)

d₂₆=0.1502

r₂₇=−125.5194

d₂₇=1.0000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=20.1000

d₂₈=8.0000 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−20.1000

d₂₉=8.2228 (wide angle edge) to 15.0177 (intermediate zoom position) to 18.5215 (telephoto edge)

r₃₀=−18.3070

d₃₀=0.6000 nd₁₈=1.80610 υd₁₈=33.27

r₃₁=78.3700

d₃₁=2.1531 nd₁₉=1.92286 υd₁₉=20.88

r₁₂=−25.6495

d₃₂=0.8000

r₃₃=∞

d₃₃=2.2000 nd₂₀=1.51680 υd₂₀=64.20

r₃₄=∞

d₃₄=5.0014 (wide angle edge) to 5.0169 (intermediate zoom position) to 4.9946 (telephoto edge)

r₃₅=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=−16.9314, A=1.77203×10⁻⁵, B=−1.88816×10⁻⁸, C=−1.37289×10⁻¹¹, D=8.40961×10⁻¹⁴

(twenty-second plane)

K=−0.4655, A=−1.30488×10⁻⁶, B=−7.35853×10⁻⁸, C=4.47932×10⁻¹⁰, D=−1.92734×10⁻¹²

(twenty-fifth plane)

K=−0.1215, A=−2.29865×10⁻⁵, B=1.22648×10⁻⁷, C=−9.70568×10⁻¹⁰, D=1.17703×10⁻¹¹

(twenty-sixth plane)

K=0.7178, A=3.15598×10⁻⁵, B=7.93060×10⁻⁸, C=−7.35002×10⁻¹⁰, D=1.18983×10⁻¹¹

FIG. 4 is a diagram of various types of aberration of the zoom lens according to the second example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 4 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.

FIG. 5 is a cross sectional view (along the optical axis) of a zoom lens according to a third example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G₃₁, a negative second lens group G₃₂, a positive third lens group G₃₃, a positive fourth lens group G₃₄, a positive fifth lens group G₃₅, and a negative sixth lens group G₃₆. Further, the diaphragm STP is disposed between the second lens group G₃₂ and the third lens group G₃₃. The cover glass CG (or filter) is disposed between the sixth lens group G₃₆ and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₃₁ includes, sequentially from the object side, a negative lens L₃₁₁, a positive lens L₃₁₂, a positive lens L₃₁₃, and a positive lens L₃₁₄. The negative lens L₃₁₁ and the positive lens L₃₁₂ are cemented together.

The second lens group G₃₂ includes, sequentially from the object side, a negative lens L₃₂₁, a negative lens L₃₂₂, a positive lens L₃₂₃, and a negative lens L₃₂₄. The negative lens L₃₂₂ and the positive lens L₃₂₃ are cemented together. Further, a surface on the object side of the negative lens L₃₂₁ is formed to be aspheric.

The third lens group G₃₃ includes, sequentially from the object side, a positive lens L₃₃₁ and a negative lens L₃₃₂ that are cemented together.

The fourth lens group G₃₄ includes, sequentially from the object side, a positive lens L₃₄₁, a positive lens L₃₄₂, and a negative lens L₃₄₃. A surface on the object side of the positive lens L₃₄₂ is aspheric. Further, the positive lens L₃₄₂ and the negative lens L₃₄₃ are cemented together.

The fifth lens group G₃₅ includes, sequentially from the object side, a positive lens L₃₅₁, a negative lens L₃₅₂, and a positive lens L₃₅₃. Both surfaces of the positive lens L₃₅₁ are aspheric. Further, the negative lens L₃₅₂ and the positive lens L₃₅₃ are cemented together.

The sixth lens group G₃₆ includes, sequentially from the object side, a negative lens L₃₆₁ and a positive lens L₃₆₂ that are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₃₂, the third lens group G₃₃, and the fourth lens group G₃₄ along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G₃₅ along the optical axis. The first lens group G₃₁ and the sixth lens group G₃₆ remain fixed.

Various values related to the zoom lens according to the third example are indicated below.

focal length of entire zoom lens=8.35 (wide angle edge) to 22.75 (intermediate zoom position) to 60.1 (telephoto edge) F number=2.25 angle of view (2ω)=70.53° (wide angle edge) to 27.68° (intermediate zoom position) to 10.70° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=63.719 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=71.544 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=65.961 focal length (FW) of entire optical system for infinity at wide angle edge=8.35

(SLM−(SLW+SLT)/2)/FW=0.803 (Values Related to Conditional Expression (2))

F14t=−213.922

(Values Related to Conditional Expression (3))

deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₃₂=0.571 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₃₂=29.500

S10/H=0.019

r₁=148.6615

d₁=1.6500 nd₁=1.80610 υd₁=33.27

r₂=61.1938

d₂=9.6601 nd₂=1.49700 υd₂=81.61

r₃=674.9250

d₃=0.1500

r₄=64.5400

d₄=6.4576 nd₃=1.49700 υd₃=81.61

r₅=257.1029

d₅=0.1500

r₆=59.8878

d₆=5.3883 nd₄=1.61800 υd₄=63.39

r₇=167.5508

d₇=0.9000 (wide angle edge) to 26.2588 (intermediate zoom position) to 43.4318 (telephoto edge)

r₈=306.7263 (aspheric surface)

d₈=0.2500 nd₅=1.53610 υd₅=41.00

r₉=108.4733

d₉=1.2000 nd₆=1.88300 υd₆=40.80

r₁₀=14.5265

d₁₀=7.8961

r₁₁=−25.8103

d₁₁=1.0000 nd₇=1.49700 υd₇=81.61

r₁₂=25.8103

d₁₂=5.2867 nd₈=1.90366 υd₈=31.31

r₁₃=−39.5598

d₁₃=1.3138

r₁₄=−24.5665

d₁₄=0.8000 nd₉=1.48′749 υd₉=70.44

r₁₅=62.0539

d₁₅=47.7845 (wide angle edge) to 14.5972 (intermediate zoom position) to 3.0080 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.2000

r₁₇=49.1025

d₁₇=4.3624 nd₁₀=1.61800 υd₁₀=63.39

r₁₈=−16.3370

d₁₈=0.8000 nd₁₁=1.56732 υd₁₁=42.84

r₁₉=66.0271

d₁₉=1.9335 (wide angle edge) to 9.7620 (intermediate zoom position) to 4.1799 (telephoto edge)

r₂₀=19.0834

d₂₀=2.9583 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=68.4183

d₂₁=0.1500

r₂₂=28.8247 (aspheric surface)

d₂₂=2.8694 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=−100.6680

d₂₃=0.8000 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=17.4858

d₂₄=13.3625 (wide angle edge) to 8.0360 (intermediate zoom position) to 5.8027 (telephoto edge)

r₂₅=17.5351 (aspheric surface)

d₂₅=5.0724 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−33.4907 (aspheric surface)

d₂₆=1.2961

r₂₇=−97.1180

d₂₇=1.0000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=18.8323

d₂₈=7.7198 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−18.8323

d₂₉=8.3857 (wide angle edge) to 13.7122 (intermediate zoom position) to 15.9455 (telephoto edge)

r₃₀=−14.8301

d₃₀=0.8000 nd₁₈=1.80610 υd₁₈=33.27

r₃₁=875.2519

d₃₁=3.0000 nd₁₉=1.92286 υd₁₉=20.88

r₃₂=−19.0866

d₃₂=0.5000

r₃₃=∞

d₁₃=1.0000 nd₂₀=1.51680 υd₂₀=64.20

r₃₄=∞

d₃₄=4.4800 (wide angle edge) to 4.5124 (intermediate zoom position) to 4.4780 (telephoto edge)

r₃₅=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=326.5969, A=1.45864×10⁻⁵, B=−3.27413×10⁻⁸, C=8.21551×10⁻¹¹, D=−1.78052×10⁻¹³

(twenty-second plane)

K=−1.0471, A=−6.42643×10⁻⁶, B=−5.52441×10⁻⁸, C=4.13340×10⁻¹⁰, D=−1.57709×10⁻¹²

(twenty-fifth plane)

K=−0.1413, A=−2.40303×10⁻⁵, B=1.28161×10⁻⁷, C=−1.08450×10⁻⁹, D=3.69783×10⁻¹²

(twenty-sixth plane)

K=0.1817, A=3.28626×10⁻⁵, B=1.15663×10⁻⁷, C=−1.39748×10⁻⁹, D=5.65410×10⁻¹²

FIG. 6 is a diagram of various types of aberration of the zoom lens according to the third example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 6 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.

FIG. 7 is a cross sectional view (along the optical axis) of a zoom lens according to a fourth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G₄₁, a negative second lens group G₄₂, a positive third lens group G₄₃, a positive fourth lens group G₄₄, and a positive fifth lens group G₄₅. Further, the diaphragm STP is disposed between the second lens group G₄₂ and the third lens group G₄₃. The cover glass CG (or filter) is disposed between the fifth lens group G₄₅ and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₄₁ includes, sequentially from the object side, a negative lens L₄₁₁, a positive lens L₄₁₂, a positive lens L₄₁₃, and a positive lens L₄₁₄. The negative lens L₄₁₁ and the positive lens L₄₁₂ are cemented together.

The second lens group G₄₂ includes, sequentially from the object side, a negative lens L₄₂₁, a negative lens L₄₂₂, a positive lens L₄₂₃, and a negative lens L₄₂₄. The positive lens L₄₂₃ and the negative lens L₄₂₄ are cemented together. Further, a surface on the object side of the negative lens L₄₂₁ is aspheric.

The third lens group G₄₃ includes, sequentially from the object side, a positive lens L₄₃₁ and a negative lens L₄₃₂ that are cemented together.

The fourth lens group G₄₄ includes, sequentially from the object side, a positive lens L₄₄₁, a positive lens L₄₄₂, and a negative lens L₄₄₃. A surface on the object side of the positive lens L₄₄₂ is aspheric. Further, the positive lens L₄₄₂ and the negative lens L₄₄₃ are cemented together.

The fifth lens group G₄₅ includes, sequentially from the object side, a positive lens L₄₅₁, a negative lens L₄₅₂, and a positive lens L₄₅₃. Both surfaces of the positive lens L₄₅₁ are aspheric. Further, the negative lens L₄₅₂ and the positive lens L₄₅₃ are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₄₂ and the fourth lens group G₄₄ along the optical axis. At this time, the diaphragm STP is also moved. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G₄₅ along the optical axis. The first lens group G₄₁ and the third lens group G₄₃ remain fixed.

Various values related to the zoom lens according to the fourth example are indicated below.

focal length of entire zoom lens=8.14 (wide angle edge) to 22.75 (intermediate zoom position) to 60.60 (telephoto edge) F number=2.85

angle of view (2ω)=72.42° (wide angle edge) to 27.47° (intermediate zoom position) to 10.66° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=58.376 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=65.379 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=58.356 focal length (FW) of entire optical system for infinity at wide angle edge=8.14

(SLM−(SLW+SLT)/2)/FW=0.861 (Values Related to Conditional Expression (2))

F14t=−218.45

(Values Related to Conditional Expression (3))

deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₄₂=0.307 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₄₂=27.420

S10/H=0.011

r₁=319.7966

d₁=1.6500 nd₁=1.90366 υd₁=31.31

r₂=72.5656

d₂=10.7848 nd₂=1.49700 υd₂=81.61

r₃=−311.7970

d₃=0.1497

r₄=64.5319

d₄=7.9428 nd₃=1.49700 υd₃=81.61

r₅=517.6623

d₅=0.1504

r₆=62.9561

d₆=4.8145 nd₄=1.83481 υd₄=42.72

r₇=125.2065

d₇=1.0515 (wide angle edge) to 28.3835 (intermediate zoom position) to 46.0511 (telephoto edge)

r₈=202.1496 (aspheric surface)

d₈=0.3000 nd₅=1.53610 υd₅=41.20

r₉=158.8874

d₈=1.2000 nd₆=1.88300 υd₆=40.80

r₁₀=13.6525

d₁₀=7.7684

r₁₁=−22.2902

d₁₁=0.8000 nd₇=1.49700 υd₇=81.61

r₁₂=28.9611

d₁₂=1.8315

r₁₃=34.0302

d₁₃=5.2187 nd₈=1.88300 υd₈=40.80

r₁₄=−27.8585

d₁₄=0.7997 nd₉=1.49700 υd₉=81.61

r₁₅=85.7544

d₁₅=47.1745 (wide angle edge) to 12.8409 (intermediate zoom position) to 2.1755 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.0013 (wide angle edge) to 10.0026 (intermediate zoom position) to 3.0001 (telephoto edge)

r₁₇=48.7738

d₁₇=1.4336 nd₁₀=1.72916 υd₁₀=54.67

r₁₈=−150.0000

d₁₈=0.8000 nd₁₁=1.64769 υd₁₁=33.84

r₁₉=52.3545

d₁₉=5.1946 (wide angle edge) to 3.0000 (intermediate zoom position) to 2.00334 (telephoto edge)

r₂₀=16.0966

d₂₀=2.1227 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=51.9417

d₂₁=0.1500

r₂₂=20.9928 (aspheric surface)

d₂₂=3.0358 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=−54.8038

d₂₃=1.4774 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=12.8327

d₂₄=8.0538 (wide angle edge) to 6.4772 (intermediate zoom position) to 7.0282 (telephoto edge)

r₂₅=16.9803 (aspheric surface)

d₂₅=4.8893 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−38.2034 (aspheric surface)

d₂₆=0.1499

r₂₇=−101.4054

d₂₇=0.8000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=22.1937

d₂₈=7.0000 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−19.4717

d₂₉=13.2585 (wide angle edge) to 17.0370 (intermediate zoom position) to 17.4265 (telephoto edge)

r₃₀=∞

d₃₀=2.0000 nd₁₈=1.51680 υd₁₈=64.20

r₃₁=∞

d₃₁=5.0092 (wide angle edge) to 5.0029 (intermediate zoom position) to 5.0090 (telephoto edge)

r₃₂=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=−475.5474, A=2.30384×10⁻⁵, B=−9.02107×10⁻⁸, C=2.44012×10⁻¹⁰, D=−3.43957×10⁻¹³

(twenty-second plane)

K=−0.1382, A=3.54823×10⁻⁶, B=−7.49188×10⁻⁸, C=1.47759×10⁻⁹, D=−1.06171×10⁻¹¹

(twenty-fifth plane)

K=−0.2034, A=−2.79047×10⁻⁵, B=9.40720×10⁻⁸, C=−2.20786×10⁻⁹, D=1.32509×10⁻¹¹

(twenty-sixth plane)

K=−0.7196, A=3.44659×10⁻⁵, B=−1.31505×10⁻⁸, C=−1.47468×10⁻⁹, D=1.07727×10⁻¹¹

FIG. 8 is a diagram of various types of aberration of the zoom lens according to the fourth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 8 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.

FIG. 9 is a cross sectional view (along the optical axis) of a zoom lens according to a fifth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G₅₁, a negative second lens group G₅₂, a positive third lens group G₅₃, a positive fourth lens group G₅₄, and a positive fifth lens group G₅₅. Further, the diaphragm STP is disposed between the second lens group G₅₂ and the third lens group G₅₃. The cover glass CG (or filter) is disposed between the fifth lens group G₅₅ and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₅₁ includes, sequentially from the object side, a negative lens L₅₁₁, a positive lens L₅₁₂, a positive lens L₅₁₃, and a positive lens L₅₁₄. The negative lens L₅₁₁ and the positive lens L₅₁₂ are cemented together.

The second lens group G₅₂ includes, sequentially from the object side, a negative lens L₅₂₁, a negative lens L₅₂₂, a positive lens L₅₂₃, and a negative lens L₅₂₄. The positive lens L₅₂₃ and the negative lens L₅₂₄ are cemented together. Further, a surface on the object side of the negative lens L₅₂₁ is aspheric.

The third lens group G₅₃ includes, sequentially from the object side, a positive lens L₅₃₁ and a negative lens L₅₃₂ that are cemented together.

The fourth lens group G₅₄ includes, sequentially from the object side, a positive L₅₄₁, a positive lens L₅₄₂, and a negative lens L₅₄₃. A surface on the object side of the positive lens L₅₄₂ is aspheric. Further, the positive lens L₅₄₂ and the negative lens L₅₄₃ are cemented together.

The fifth lens group G₅₅ includes, sequentially from the object side, a positive lens L₅₅₁, a negative lens L₅₅₂, and a positive lens L₅₅₃. Both surfaces of the positive lens L₅₅₁ are aspheric. Further, the negative lens L₅₅₂ and the positive lens L₅₅₃ are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₅₂, the third lens group G₅₃, and the fourth lens group G₅₄ along the optical axis. Furthermore, zooms lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G₅₅ along the optical axis. The first lens group G₅₁ remains fixed.

Various values related to the zoom lens according to the fifth example are indicated below.

focal length of entire zoom lens=7.80 (wide angle edge) to 22.75 (intermediate zoom position) to 58.04 (telephoto edge) F number=2.85 angle of view (2ω)=74.29° (wide angle edge) to 27.90° (intermediate zoom position) to 11.22° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=53.038 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=63.160 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=54.477 focal length (FW) of entire optical system for infinity at wide angle edge=7.80

(SLM−(SLW+SLT)/2)/FW=1.205 (Values Related to Conditional Expression (2))

F14t=−222.24 (Values Related to Conditional Expression (3)) deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₅₂=0.354 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₅₂=29.700

S10/H=0.012

r₁=282.5658

d₁=1.6500 nd₁=1.90366 υd₁=31.31

r₂=71.7229

d₂=11.1441 nd₂=1.49700 υd₂=81.61

r₃=−269.6826

d₃=0.1500

r₄=58.2686

d₄=7.4164 nd₃=1.49700 υd₃=81.61

r₅=258.2745

d₅=0.1500

r₆=60.2403

d₆=4.2271 nd₄=1.88300 υd₄=40.80

r₇=101.8945

d₇=0.9000 (wide angle edge) to 27.8306 (intermediate zoom position) to 45.9000 (telephoto edge)

r₈=111.4890 (aspheric surface)

d₈=0.3000 nd₅=1.53610 υd₅=41.20

r₉=93.8724

d₉=1.2000 nd₆=1.88300 υd₆=40.80

r₁₀=13.2527

d₁₀=8.8423

r₁₁=−21.3522

d₁₁=0.8000 nd₇=1.49700 υd₇=81.61

r₁₂=28.9461

d₁₂=1.2651

r₁₃=31.9998

d₁₃=5.6440 nd₈=1.88300 υd₈=40.80

r₁₄=−28.3373

d₁₄=0.8000 nd₉=1.49700 υd₉=81.61

r₁₅=80.7396

d₁₅=48.6273 (wide angle edge) to 11.5723 (intermediate zoom position) to 2.1726 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.0000

r₁₇=90.9268

d₁₇=1.6008 nd₁₀=1.77250 υd₁₀=49.62

r₁₈=−50.0000

d₁₈=0.8000 nd₁₁=1.62004 υd₁₁=36.30

r₁₉=82.9067

d₁₉=1.5000 (wide angle edge) to 7.2696 (intermediate zoom position) to 1.5000 (telephoto edge)

r₂₀=15.4903

d₂₀=2.1378 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=33.7803

d₂₁=0.1500

r₂₂=16.2526 (aspheric surface)

d₂₂=2.9662 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=−104.1231

d₂₃=1.4133 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=11.8086

d₂₄=8.4563 (wide angle edge) to 8.2596 (intermediate zoom position) to 5.9201 (telephoto edge)

r₂₅=16.0302 (aspheric surface)

d₂₅=5.7946 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−38.5894 (aspheric surface)

d₂₆=0.1500

r₂₇=−113.2219

d₂₇=0.8000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=22.6876

d₂₈=6.0000 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−20.1597

d₂₉=11.2692 (wide angle edge) to 15.8183 (intermediate zoom position) to 15.2442 (telephoto edge)

r₃₀=∞

d₃₀=2.0000 nd₁₈=1.51680 υd₁₈=64.20

r₃₁=∞

d₃₁=5.0000

r₃₂=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=−137.2586, A=2.62265×10⁻⁵, B=−9.31163×10⁻⁸, C=2.21275×10⁻¹⁰, D=−2.81522×10⁻¹³

(twenty-second plane)

K=−0.0855, A=5.22861×10⁻⁶, B=−6.95276×10⁻⁸, C=1.84884×10⁻⁹, D=−1.44193×10⁻¹¹

(twenty-fifth plane)

K=−0.2776, A=−3.12577×10⁻⁵, B=8.20931×10⁻⁸, C=−1.91427×10⁻⁹, D=1.61775×10⁻¹¹

(twenty-sixth plane)

K=−0.6048, A=3.43639×10⁻⁵, B=−7.14301×10⁻⁸, C=−1.47690×10⁻⁹, D=1.55904×10⁻¹¹

FIG. 10 is a diagram of various types of aberration of the zoom lens according to the fifth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 10 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.

FIG. 11 is a cross sectional view (along the optical axis) of a zoom lens according to a sixth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G₆₁, a negative second lens group G₆₂, a positive third lens group G₆₃, a positive fourth lens group G₆₄, a positive fifth lens group G₆₅, and a negative sixth lens group G₆₆. Further, the diaphragm STP is disposed between the second lens group G₆₂ and the third lens group G₆₃. The cover glass CG (or filter) is disposed between the sixth lens group G₆₆ and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.

The first lens group G₆₁ includes, sequentially from the object side, a negative lens L₆₁₁, a positive lens L₆₁₂, a positive lens L₆₁₃, and a positive lens L₆₁₄. The negative lens L₆₁₁ and the positive lens L₆₁₂ are cemented together.

The second lens group G₆₂ includes, sequentially from the object side, a negative lens L₆₂₁, a negative lens L₆₂₂, a positive lens L₆₂₃, and a negative lens L₆₂₄. The negative lens L₆₂₂ and the positive lens L₆₂₃ are cemented together. Further, a surface on the object side of the negative lens L₆₂₁ is aspheric.

The third lens group G₆₃ includes, sequentially from the object side, a positive lens L₆₃₁ and a negative lens L₆₃₂ that are cemented together.

The fourth lens group G₆₄ includes, sequentially from the object side, a positive L₆₄₁, a positive lens L₆₄₂, and a negative lens L₆₄₃. A surface on the object side of the positive lens L₆₄₂ is aspheric. Further, the positive lens L₆₄₂ and the negative lens L₆₄₃ are cemented together.

The fifth lens group G₆₅ includes, sequentially from the object side, a positive lens L₆₅₁, a negative lens L₆₅₂, and a positive lens L₆₅₃. Both surfaces of the positive lens L₆₅₁ are aspheric. Further, the negative lens L₆₅₂ and the positive lens L₆₅₃ are cemented together.

The sixth lens group G₆₆ includes, sequentially from the object side, a negative lens L₆₆₁ and a positive lens L₆₆₂ that are cemented together.

The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G₆₂ and the third lens group G₆₃ along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom, by moving the fifth lens group G₆₅ along the optical axis. The first lens group G₆₁, the fourth lens group G₆₄, and the sixth lens group G₆₆ remain fixed.

Various values related to the zoom lens according to the sixth example are indicated below.

focal length of entire zoom lens=8.38 (wide angle edge) to 22.75 (intermediate zoom position) to 62.39 (telephoto edge) F number=2.85 angle of view (2ω)=70.28° (wide angle edge) to 27.57° (intermediate zoom position) to 10.30° (telephoto edge)

(Values Related to Conditional Expression (1))

distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=63.190 distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=74.408 distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=62.659 focal length (FW) of entire optical system for infinity at wide angle edge=8.38

(SLM−(SLW+SLT)/2)/FW=1.370 (Values Related to Conditional Expression (2))

F14t=−265.26

(Values Related to Conditional Expression (3))

deviation (S10) of paraxial curvature radius and aspheric shape at height that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₆₂=0.544 height (H) that is 10% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G₆₂=30.100

S10/H=0.018

r₁=138.8718

d₁=1.6500 nd₁=1.80610 υd₁=33.27

r₂=61.9153

d₂=8.5663 nd₂=1.49700 υd₂=81.61

r₃=1028.2950

d₃=0.1500

r₄=60.3545

d₄=6.3671 nd₃=1.49700 υd₃=81.61

r₅=295.8558

d₅=0.1500

r₆=65.2190

d₆=4.1407 nd₄=1.61800 υd₄=63.39

r₇=139.5672

d₇=0.9000 (wide angle edge) to 25.2786 (intermediate zoom position) to 44.9569 (telephoto edge)

r₈=262.0586 (aspheric surface)

d₈=0.3000 nd₅=1.53610 υd₅=41.21

r₉=138.6589

d₉=1.2000 nd₆=1.88300 υd₆=40.80

r₁₀=16.2318

d₁₀=7.7691

r₁₁=−26.5932

d₁₁=1.0000 nd₇=1.49700 υd₇=81.61

r₁₂=26.5932

d₁₂=5.5008 nd₈=1.90366 υd₈=31.31

r₁₃=−36.2017

d₁₃=1.2996

r₁₄=−23.2275

d₁₄=0.8000 nd₉=1.48749 υd₉=70.44

r₁₅=38.1766

d₁₅=47.0041 (wide angle edge) to 11.4261 (intermediate zoom position) to 3.4734 (telephoto edge)

r₁₆=∞ (diaphragm)

d₁₆=3.2000

r₁₇=47.7891

d₁₇=3.0763 nd₁₀=1.61800 υd₁₀=63.89

r₁₈=−16.0874

d₁₈=0.8000 nd₁₁=1.56732 υd₁₁=42.84

r₁₉=96.4756

d₁₉=4.7246 (wide angle edge) to 15.9240 (intermediate zoom position) to 4.1984 (telephoto edge)

r₂₀=18.3644

d₂₀=2.4991 nd₁₂=1.84666 υd₁₂=23.78

r₂₁=59.3603

d₂₁=0.1500

r₂₂=28.9811 (aspheric surface)

d₂₂=2.6325 nd₁₃=1.61800 υd₁₃=63.39

r₂₃=−104.8188

d₂₃=0.8000 nd₁₄=1.90366 υd₁₄=31.31

r₂₄=16.9149

d₂₄=12.7613 (wide angle edge) to 6.7184 (intermediate zoom position) to 5.8228 (telephoto edge)

r₂₅=17.1503 (aspheric surface)

d₂₅=6.1084 nd₁₅=1.61800 υd₁₅=63.39

r₂₆=−34.1345 (aspheric surface)

d₂₆=0.1538

r₂₇=−111.6006

d₂₇=1.0000 nd₁₆=1.90366 υd₁₆=31.31

r₂₈=19.4748

d₂₈=6.9286 nd₁₇=1.45650 υd₁₇=90.27

r₂₉=−19.4749

d₂₉=8.2678 (wide angle edge) to 14.3106 (intermediate zoom position) to 15.2062 (telephoto edge)

r₃₀=−14.0575

d₃₀=0.8000 nd₁₈=1.80610 υd₁₈=33.27

r₃₁=160.0140

d₃₁=3.0000 nd₁₉=1.92286 υd₁₉=20.88

r₃₂=−18.9554

d₃₂=2.2900

r₃₃=∞

d₃₃=1.0000 nd₂₀=1.51680 υd₂₀=64.20

r₃₄=∞

d₃₄=2.9983 (wide angle edge) to 3.0167 (intermediate zoom position) to 2.9932 (telephoto edge)

r₃₅=∞ (imaging plane) constant of cone (K) and aspheric coefficients (A, B, C, D) (eighth plane)

K=235.8261, A=9.85751×10⁻⁶, B=−1.48380×10⁻⁸, C=2.78366×10⁻¹¹, D=−3.08842×10⁻¹⁴

(twenty-second plane)

K=−0.8891, A=−4.81420×10⁻⁶, B=−1.21584×10⁻⁷, C=1.73658×10⁻⁹, D=−1.08127×10⁻¹¹

(twenty-fifth plane)

K=−0.1835, A=−2.65316×10⁻⁵, B=1.26633×10⁻⁷, C=−1.04068×10⁻⁹, D=−1.23932×10⁻¹²

(twenty-sixth plane)

K=0.4017, A=3.09450×10⁻⁵, B=1.21550×10⁻⁷, C=−1.69140×10⁻⁹, D=2.67818×10⁻¹²

FIG. 12 is a diagram of various types of aberration of the zoom lens according to the sixth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 12 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.

Among the values for each of the examples above, r₁, r₂, . . . indicate radii of curvature for each lens, diaphragm surface, etc.; d₁, d₂, . . . indicate the thickness of the lenses, diaphragm, etc. or the distance between surfaces thereof; nd₁, nd₂, . . . indicates the refraction index of each lens with respect to the d-line (λ=587.56 nm); υd₁, υd₂, . . . indicates the Abbe number with respect to the d-line (λ=587.56 nm) of each lens.

Each of the aspheric surfaces above can be expressed by equation [1], where Z=the depth of the aspheric surface, y=the height from the optical axis, and the direction of travel of light is positive.

$\begin{matrix} {Z = {\frac{y^{2}}{{R\left( {1 + \sqrt{1 + {\left( {1 + K} \right){y/R^{2}}}}} \right)}^{2}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + D^{10}}} & \lbrack 1\rbrack \end{matrix}$

And where, R is paraxial radii of curvature; K is constant of the cone; and A, B, C, D are the fourth, sixth, eighth, and tenth aspheric coefficients, respectively.

As described above, the zoom lens according to each of the examples above satisfies conditional expressions (1) and (2), whereby diameter reduction, a wide angle of view (70° or more), and maintenance of the F number at a constant value or below (2.9 or less) over the entire zoom range is achieved, making the zoom lens a large diameter zoom lens that is capable of high zoom rations (6 or more). Further, by forming a surface on the object side of the lens farthest on the object side in the second lens group, to be an aspheric surface that satisfies conditional expression (3) above, various types of aberration can be effectively corrected over the entire zoom range without sacrificing the compactness of the optical system.

Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth. 

What is claimed is:
 1. A zoom lens comprising, sequentially from an object side: a positive first lens group; a negative second lens group; a diaphragm; a positive third lens group; a positive fourth lens group; and a positive fifth lens group, wherein a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied, SLW being a distance from the diaphragm at a wide angle edge to an imaging plane, SLM being a distance from the diaphragm at an intermediate zoom position to the imaging plane, SLT being a distance from the diaphragm at a telephoto edge to the imaging plane, FW being optical system focal length for infinity at the wide angle edge, and F14t being a combined focal length for the first to the fourth lens groups at the telephoto edge.
 2. The zoom lens according to claim 1, wherein in the second lens group, a lens farthest on the object side among lenses in the second lens group, has on the object side, an aspheric surface satisfying a third condition S10/H≧0.005, S10 being deviation of paraxial curvature radius and aspheric shape at a height that is 10% of an effective diameter of the aspheric surface and H being 10% of the effective diameter of the aspheric surface. 